- Eliminate unused second parameter values.
- Switch to getTabUrl for PDF linking.

- Resolves VUFIND-1328.

- Currently not used in core logic, but useful for some institutions' local subclasses.

- When generating OAI dates, make sure they are always in UTC.
- Also add some tolerance to default 'until' date in case of minor inconsistencies in indexing process.

Fix in KohaILSDI getPurchaseHistory function in order to get as
a result an array of ALL recieved issues of a serial.
(This behavior better matches the function documentation and is
consisntent with getPurchaseHistory results from other ILS drivers)
In case one wants to limit the number of displayed issues, this
should be ideally handled in the theme template.

- Includes renaming of getHoldingFields support method to extractFieldsFromApiData for clarity.

- Also lengthen renewal window for easier testing.

- Add support for fetching summary holdings from Sierra when using the REST API.
- Includes a fix for ordering of results.
- Introduces a new "pseudo-version" of the API (5.1) which is currently disabled by default (not supported in all installations at this time). This version must be activated to allow summary holdings support.